The field of the disclosure relates generally to appliance protection systems and more specifically to systems and methods for protecting an appliance junction from the high heat and current of an over-current/over-temperature event.
In residential electrical wiring, three-wire 220/240 Volt circuits (referred to herein as 240 Volt circuit) are conventionally employed for large consumer appliances. Appliances which use current from a 240 Volt circuit (such as electric water heaters and air conditioners) also have three wires. A black wire, often known as the first “hot” wire, supplies current at 120 volts from a power source (e.g., a public utility or an electrical generator) to an electrical load (e.g., a compressor motor, a pump motor, or a heating element depending on the type of appliance) connected to the power source. A second “hot” wire, which may be blue, red, or white, also supplies current in to the load at 120 volts.
The first and second hot wires connect to the load at an electrical junction typically having three pins. Such an electrical junction is also interchangeably referred to herein as an appliance junction, or simply a junction. The first and second hot wires connect to first and second pins of the junction, respectively. A third wire, called a “common” wire serves the function of completing the electrical circuit back to the power source. The third wire connects to a third pin of the junction.
A temperature limiting or regulating device is conventionally attached only to the first hot wire for providing protection against over-current events. More specifically, each pin of the junction includes a metal wire insulated by glass. During an over-current or over-temperature event, the insulating glass may heat up and melt or otherwise fail. Known temperature limiting and regulating devices typically include a trip unit that controls the flow of current to the junction inside the appliance based upon temperature or current level flowing through the device. More specifically, the trip unit causes current flowing through the circuit breaker to be interrupted if the temperature or current is outside of acceptable conditions.
In conventional 220/240 Volt appliances employing electrical loads, such as a compressor in an air conditioner, the electrical junction pins (e.g., FUSITE® pins) (“Fusite” is a registered trademark of Emerson Electric Co. of St. Louis, Mo.) on the compressor are isolated from the compressor shell (ground) by the glass insulator. The glass insulator also provides a hermetic seal between the junction and the pressurized compressor shell. An overload protection device is commonly employed to protect the first pin of a three pin 240V junction from damage by the high heat of an over-current or over-temperature event to satisfy UL requirements. The second pin is left unprotected because the UL standard does not require the second pin to be protected and protection on the second pin increases the cost of the appliance. An over-current or -temperature event could cause a failure of the insulating glass associated with the second pin, which may cause the second pin to short to the grounded compressor shell and fail. If the glass insulator on the second pin melts or otherwise deforms during the over-temperature conduction, oil and/or other liquids may be released from the pressurized compressor shell. As such, it is desirable to protect the junction to facilitate preventing failure of the pins of the junctions.